Flood prevention work continues in Portland’s Lents neighborhood

The second phase of the east Lents floodplain restoration project is expected to help decrease flooding of Johnson Creek onto Southeast Foster Road. (Photo by Sam Tenney/DJC)

Johnson Creek in the past has flooded Southeast Portland about two out of every three years, adding as much as 30 inches of standing water each time. But after a city project wraps up, flooding is expected to occur only once every three years.

Work began on the 52-acre property surrounding Johnson Creek last summer as part of the east Lents floodplain restoration project to reduce flooding onto Southeast Foster Road and improve the area’s natural habitat for wildlife.

The second phase, set to start in May and cost $2.3 million, will finish the job. Much of the work will involve digging water storage areas and stabilizing stream banks, but heavy construction also is planned.

“The property has faced some pretty major negative impacts that have essentially hindered the water’s ability to go out onto the natural floodplain,” said Maggie Skenderian, Johnson Creek watershed manager with Portland’s Bureau of Environmental Services. “This (phase of the) project will get rid of some of those man-made structures and help improve the water quality.”

Skenderian said a concrete wall built in the 1930s will be torn down because it prevents the creek from displacing excess water. Also, three bridges, each approximately 25 feet wide and 60 feet long and formerly used by area residents, will be demolished.

“Anytime you introduce a man-made structure like the bridges, it will reduce the value of a natural habitat and cause erosion,” said Kevin Timmins, project manager at Otak, which designed both phases of the project. “We want to return the habitat back to how it once was.”

Timmins said the creek’s bank will be restored by packing soil in biodegradable fabric wrap with plant seeds. The plants’ roots are expected to hold the soil together, creating a natural strengthener.

To improve water quality, two water treatment facilities will be built near the outfalls that presently discharge into the creek at Foster Road.

“Many believe Johnson Creek is a lost cause and associate it with old shopping carts and tires,” Skenderian said. “But we’ve found over 1,600 … salmon in the creek, which is a very important symbol of the health of our creeks and what we hope to improve upon.”

Like the project’s first phase, the second one will present a number of construction challenges. One will involve digging 22,000 cubic yards of dirt near the banks of the creek to create storage for excess water. If not done correctly, more flooding could occur as a result.

“It’s a beautiful dance between conveyance and storage,” Skenderian said. “They have to very carefully maximize water storage without hitting groundwater and without stranding the fish – it’s very difficult.”

Timmins said he had to take into account how each project task would affect the flow of the creek.

“The project had to be designed in a way that maintained flood storage volumes without increasing flow rates to areas downstream,” he said.

Both Timmins and Skenderian said they hope this phase of construction will goes as smoothly as the first one. In January, rains caused the creek to overflow, but the water storage units dug last summer stopped the water from flowing onto Foster Road – validating the project’s purpose.

The project has faced some problems with security, though.

“Transients continue to set up camp in the project site and require the contractor to seek police assistance to have them move out of harm’s way,” Timmins said. “The installation of the fencing sometimes caused confusion for larger wildlife living in the area, so intermittent gaps had to be left in the fencing. Theft of fence panels, metal stakes and bridge guard railing has been a problem.”

Because the creek is in an industrial area that has a reputation for crime, Skenderian wonders what will happen to the property once it’s opened to the public.

“It’s going to be a challenge to create access that encourages people to go in there with their best of intentions,” she said. “The project is right next to 82nd Avenue, which is known for having people who don’t have the best relationship with the law.”

Construction will continue through fall. Peter Tapani Construction, based in Battle Ground, Wash., is the general contractor for both phases of the project.

4 comments

Maggie,
any dates for when we expect to know about the revised floodplain? I live in the floodplain, according to FEMA despite having never seen water nearby. I’d love to drop the unnecessary flood insurance!

Thanks for the nice piece on our East Lents project. I wanted to claify for folks that we saw about 1600 fish total while we did the project. It was on the order of 10 species, and over 95% of the species were native. If you are interested in knowing more about our efforts to restore salmon habitat and improve watershed health in Johnson Creek, please let me know.